P-80 Shooting Star, T-33/F-94 in Action

"Jet Propulsion: propulsion of a body produced by the forwardly directed forces of the reaction resulting from the rearward discharge from the body of a jet (a high speed stream of fluid) through a nozzle or orifice."
The theory of jet propulsion has been with us a very long time, since the second century when Hero of Alexandria created motion by rotating a metal ball on its supports by means of jets. But it wasn't until the late 1920s that the principle was applied to aircraft. In 1928 RAF Flight Cadet Frank Whittle put forth a thesis on the theory of reaction-thrust as ap­plied to aircraft gas turbines. This led to the design, development and bench testing of the Whittle jet engine In 1937. But the British government had no interest in the jet engine at that time.
In Germany, Hitler had revived the air arm and developed it to a keen edge. But the Ger­man Air Ministry also turned deaf ears on the jet engine. A civilian, Ernst Heinkel, saw something valuable in the jet engine concept. With his own money, and using an engine designed and developed by a German student named von Ohain, Heinkel instituted an air­frame and engine program that culminated in the flight of the world's first pure jet-propelled aircraft - the He178. which flew in 1939, powered by the HeS3A engine. Between the Heinkel developments and the infusion of younger, forward thinking officers in the Luftwaffe, the attitude of the Air Ministry changed. In 1938 an order was placed to develop the first jet propelled fighter aircraft - the Messerschmitt Me262.